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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1961

Wind-Tunnel Investigation of a Balloon as a Towed Decelerator at Mach Numbers from 1.47 to 2.50

A wind-tunnel investigation has been conducted to study the characteristics of a towed spherical balloon as a drag device at Mach numbers from 1.47 to 2.50, Reynolds numbers from 0.36 x 10(exp 6) to 1.0 x 10(exp 6) , and angles of attack from -15 to 15 deg. Towed spherical balloons were found to be stable at supersonic speeds. The drag coefficient of the balloon is reduced by the presence of a tow cable and a further reduction occurs with the addition of a payload. The balloon inflation pressure required to maintain an almost spherical shape is about equal to the free-stream dynamic pressure. Measured pressure and temperature distribution around the balloon alone were in fair agreement with predicted values. There was a pronounced decrease in the pressure coefficients on the balloon when attached to a tow cable behind a payload.

McShera, John T.↗
DOE OSTI2024

Evaluation of Uncertainties of Pressure Gain Measurements in Rotating Detonation Combustor

Experimentally measuring the pressure gain of a rotating detonation combustor through the method of equivalent available pressure is prone to many experimental uncertainties. A detailed analysis of sources of random and systematic uncertainties in the thrust and pressure gain is performed using data from a hydrogen/air-operated rotating detonation combustor. The combustor had an axial air inlet and a 50% exit constriction. The measured (negative) pressure gain values agree with the results in the literature for similar inlet-to-exit area ratios. The base drag correction on the centerbody was found to be the greatest source of uncertainty for the thrust. While thrust is the predominant source of random uncertainty in the pressure gain calculation, significant systematic errors can be committed due to the assumed exit Mach number. The impact of this assumption becomes more detrimental the closer to positive the measured pressure gain is. By experimentally evaluating the exit Mach number, the random and systematic uncertainty in pressure gain both decreased, indicating that this should be an essential step. A definitive demonstration of gain is challenging, given the assessed uncertainties, and recommendations are provided to increase the precision of the equivalent available pressure methodology.

Engineering↗
NASA NTRS1988

Measured and predicted pressure distributions on the AFTI/F-111 mission adaptive wing

Flight tests have been conducted using an F-111 aircraft modified with a mission adaptive wing (MAW). The MAW has variable-camber leading and trailing edge surfaces that can change the wing camber in flight, while preserving smooth upper surface contours. This paper contains wing surface pressure measurements obtained during flight tests at Dryden Flight Research Facility of NASA Ames Research Center. Upper and lower surface steady pressure distributions were measured along four streamwise rows of static pressure orifices on the right wing for a leading-edge sweep angle of 26 deg. The airplane, wing, instrumentation, and test conditions are discussed. Steady pressure results are presented for selected wing camber deflections flown at subsonic Mach numbers up to 0.90 and an angle-of-attack range of 5 to 12 deg. The Reynolds number was 26 million, based on the mean aerodynamic chord. The MAW flight data are compared to MAW wind tunnel data, transonic aircraft technology (TACT) flight data, and predicted pressure distributions. The results provide a unique database for a smooth, variable-camber, advanced supercritical wing.

Webb, Lannie D.↗
NASA NTRS1979

Shear strength measurements of lubricants at high pressure

Measurements of lubricant shear rheological behavior in the amorphous solid region and near the liquid-solid transition are reported on three lubricants under pressure. Elastic, plastic and viscous behavior was observed. The maximum yield shear stress (limiting shear stress) is a function of temperature and pressure and is believed to be the property which determines the maximum traction in elastohydrodynamic contacts such as traction drives.

Bair, S.↗
NASA NTRS1934

Pressure-Distribution Measurements on the Hull and Fins of a 1/40-Scale Model of the U. S. Airship "Akron."

This report presents the results of measurements of pressure distribution conducted in the propeller-research wind tunnel of the National Advisory Committee for Aeronautics on a 1/40-scale model of the U. S. Airship "Akron" (ZRS-4). The pressures, which were measured simultaneously at nearly 400 orifices located at 26 stations along one side of the hull, were recorded by two photographic multiple manometers placed inside the model. The hull pressures were measured both with and without the tail surfaces and the control car for eight angles of pitch varying from 0 degree to 20 degrees and at air speeds of approximately 70 and 100 miles per hour. The pressures were also measured at approximately 160 orifices on one horizontal fin for the above speeds and pitch angles and for nine elevator angles.

Freeman, Hugh B↗
NASA NTRS1978

Measurement of unsteady pressures in rotating systems

The principles of the experimental determination of unsteady periodic pressure distributions in rotating systems are reported. An indirect method is discussed, and the effects of the centrifugal force and the transmission behavior of the pressure measurement circuit were outlined. The required correction procedures are described and experimentally implemented in a test bench. Results show that the indirect method is suited to the measurement of unsteady nonharmonic pressure distributions in rotating systems.

Kienappel, K.↗
NASA NTRS1978

Pressure and velocity measurements in a three dimensional wall jet

A flat plate and a curved wall surface, intended to model a wing-flap combination in a high V/STOL configuration, were used to measure pressure and flow velocity in a freely expanding coflowing jet and a three dimensional wall jet. The effects of increasing the velocity ratio of the jet exit plane velocity to the free stream velocity were investigated. Velocity measurements were made using a two color laser Doppler velocimeter with a phase-locked loop processor. Fluctuating pressures were monitored with condenser-type microphones. Quantities measured include the width of the mixing region, the mean velocity field, turbulent intensities, and time scales. Wall and static pressure-velocity correlations and coherences are presented.

Catalano, G. D.↗
NASA NTRS1979

A technique for remotely measuring surface pressure from a satellite using a multicolor laser ranging system

The optical path length from a satellite to the earth's surface is strongly dependent on the atmospheric pressure along the propagation path. Surface pressure can be measured by using a multicolor laser ranging system to observe the change with wavelength in the optical path length from the satellite to a ground target. The equations which relate surface pressure to the differential path lengths are derived and the accuracy of the pressure measurement is evaluated in terms of the ranging system parameters. The results indicate that pressure accuracies of a few millibars appear feasible.

Gardner, C. S.↗
NASA NTRS1979

Technique for remotely measuring surface pressure from a satellite using a multicolor laser ranging system

The optical path length from a satellite to the earth's surface is strongly dependent on the atmospheric pressure along the propagation path. It is shown that surface pressures can be measured by the use of a multicolor laser ranging system to observe the change with wavelength in the optical path length from the satellite to a ground target. Equations are derived which relate surface pressure to the differential path lengths. In addition, the accuracy of the pressure measurement is evaluated in terms of the ranging system parameters. It is concluded that the results indicate that pressure accuracies of a few millibars appear feasible.

Gardner, C. S.↗
NASA NTRS1981

Measured transonic unsteady pressures on an energy efficient transport wing with oscillating control surfaces

Highlight results are presented from subsonic and transonic pressure measurement studies conducted in the Langley Transonic Dynamics Tunnel on a supercritical wing model representative of an energy efficient transport design. Steady- and unsteady-pressure data were acquired on the upper and lower wing surface at an off-design Mach number of 0.60 and at the design Mach number of 0.78, for a Reynolds number of 2.2 x 10(6) (based on the wing average chord). The model configuration consisted of a sidewall-Mounted half-body fuselage and a semi-span wing with an aspect ratio of 10.76, a leading-edge sweepback angle of 28.8 degrees, and supercritical airfoil sections. The wing is instrumented with 252 static pressure orifices and 164 dynamic pressure gages. Model test variables included wing angle of attack, control-surface mean deflection angle, control-surface oscillating deflection angle and frequency, and phasing between oscillating leading-edge and trailing-edge controls when used together.

Cazier, F. W., Jr.↗
NASA NTRS1979

Airborne pressure and temperature measurements during the 1977 intertropical convergence zone experiment

During the 1977 ITCZ (Intertropical Convergence Zone) experiment in Panama two aircraft and numerous balloon-borne radiosonde instruments were equipped to measure pressure and temperature. The experiment was a coordinated effort to evaluate the meteorological conditions that prevailed from July 17 through 31, 1977. A critical analysis of the data collected on one of the aircraft (the Lear jet) operating at altitudes to 13,000 m for about 2 hr each day during most days of the experiment is presented. The discussion includes a comparison of the vertical profiles of potential temperature obtained from the Learjet with those obtained from balloons launched at Ft. Sherman. Time histories of pressure, temperature, and potential temperature, as observed from the Learjet are also presented.

Munoz, R. M.↗
NASA NTRS2000

Low Level Pressure Oscillation Measurements in High, Varying DC Pressure Environments

Passive motor stability diagnostics require high s/n measurements of low level (60 to 80 db below mean pressure) oscillatory pressures in environments with large and varying DC pressures. Three approaches are briefly examined relative to passive diagnostic demands. Although the high pass filter approach has been demonstrated by Hessler, the 'short time constant' approach is recommended because it enables the use of sensitive p-ducers (resolutions approx. 10(exp -4) psi). Pieso-electric transducers are described and a methodology for using high sensitivity designs for passive diagnostics measurements is presented.

Glick, R. L.↗